2021年

(5) Dong-Lin Wang, Xin-Qing Xie, Shuo Fang, Shi Pu, Analytic solutions of relativistic dissipative spin hydrodynamics with radial expansion in Gubser flow, Phys.Rev.D 105 (2022) 11, 114050, arXiv: 2112.15535

We have derived the analytic solutions of dissipative relativistic spin hydrodynamics with Gubser expansion. Following the standard strategy of deriving the solutions in a Gubser flow, we take the Weyl rescaling and obtain the energy-momentum and angular momentum conservation equations in the space-time. We then derive the analytic solutions of spin density, spin potential and other thermodynamic in space-time and transform them back into Minkowski space-time . In the Minkowski space-time, the spin density and spin potential including the information of radial expansion decay as ∼tau and ∼tau in large limit, with being proper time and  being the characteristic length of the system, respectively. Moreover, we observe the nonvanishing spin corrections to the energy density and other dissipative terms in the Belinfante form of dissipative spin hydrodynamics. Our results can also be used as test beds for future simulations of relativistic dissipative spin hydrodynamics.

(4) Cong Yi, Shi Pu, Jian-Hua Gao, Di-Lun Yang, Hydrodynamic helicity polarization in relativistic heavy ion collisions, Phys.Rev.C 105 (2022) 4, 044911, arXiv: 2112.15531

We study helicity polarization through the (3+1) dimensional relativistic viscous hydrodynamic models at  200GeV Au+Au collisions. Similar to the local spin polarization, we consider the helicity polarization beyond global equilibrium and investigate the contributions induced by thermal vorticity, shear viscous tensor, and the fluid acceleration. We find that the local helicity polarization induced by thermal vorticity dominates over other contributions. It also implies that in the low-energy collisions, the the fluid vorticity as part of thermal vorticity may play the crucial role to the total helicity polarization. Such a finding could be useful for probing the local strength of vorticity in rotational quark gluon plasmas by measuring helicity polarization. Our simulation confirms the strict space reversal symmetry, whereas we also compare our numerical results with approximated relations derived from ideal Bjorken flow. Our studies also provide a baseline for the future investigation on local parity violation through the correlations of helicity polarization.

(3) Dong-Lin Wang, Shuo Fang, Shi Pu. Analytic solutions of relativistic dissipative spin hydrodynamics with Bjorken expansion. Phys.Rev.D 104 (2021) 11, 114043. arXiv:2107.11726.

We have studied analytically the longitudinally boost-invariant motion of a relativistic dissipative fluid with spin. We have derived the analytic solutions of spin density and spin chemical potential as a function of proper time \tau in the presence of the viscous tensor and the second order relaxation time corrections for spin. Interestingly, analogous to the ordinary particle number density and chemical potential, we find that the spin density and spin chemical potential decay as \tau^-1 and \tau^-{1/3}, respectively. These solutions can serve both to gain insight on the dynamics of spin polarization in relativistic heavy-ion collisions and as test beds for further numerical codes.

(2) Ren-jie Wang, Shi Pu, Qun Wang. Lepton pair production in ultraperipheral collisions. Phys.Rev.D 104 (2021) 5, 056011. arXiv:2106.05462.

The lepton pair production in ultraperipheral collisions is studied in the classical field approximation. We derive a general form of the cross section in terms of photon distributions that depend on the transverse momentum and coordinate based on the wave packet form of nuclear wave functions. Such a general form of the cross section in the classical field approximation contains the results of the generalized equivalent photon approximation (EPA) as well as the corrections beyond EPA in the Born approximation. By rewriting the general form of the cross section in light-cone coordinates, we find a good connection with the transverse momentum dependent distribution factorization formalism in the Born approximation. Our numerical results are consistent with current experimental data.

(1) Cong Yi, Shi Pu, Di-Lun Yang. Reexamination of local spin polarization beyond global equilibrium in relativistic heavy ion collisions. Phys.Rev.C 104 (2021) 6, 064901. arXiv:2106.00238.

We study local spin polarization in the relativistic hydrodynamic model. Generalizing the Wigner functions previously obtained from chiral kinetic theory by Y. Hidaka et al. [Phys. Rev. D 97, 016004 (2018)] to the massive case, we present the possible contributions up to the order of hbar from thermal vorticity, shear viscous tensor, other terms associated with the temperature and chemical-potential gradients, and electromagnetic fields to the local spin polarization. We then implement the (3+1)-dimensional viscous hydrodynamic model to study the spin polarizations from these sources with a small chemical potential and ignorance of electromagnetic fields by adopting an equation of state different from those in other recent studies. Although the shear correction alone upon the local polarization results in a sign and azimuthal-angle dependence more consistent with experimental observations, as also discovered in other recent studies, it is mostly suppressed by the contributions from thermal vorticity and other terms that yield an opposite trend. It is found that the total local spin polarization can be very sensitive to the equation of states, the ratio of shear viscosity to entropy density, and the freeze-out temperature.